Janet A. Sawicki

Claudin-3 gene silencing with siRNA suppresses ovarian tumor growth and metastasis

Claudin-3 (CLDN3) is a tight junction protein that is overexpressed in 90% of ovarian tumors. Previous in vitro studies have indicated that CLDN3 overexpression promotes the migration, invasion, and survival of ovarian cancer cells. Here, we investigated the efficacy of lipidoid-formulated CLDN3 siRNA in 3 different ovarian cancer models. Intratumoral injection of lipidoid/CLDN3 siRNA into OVCAR-3 xenografts resulted in dramatic silencing of CLDN3, significant reduction in cell proliferation, reduction in tumor growth, and a significant increase in the number of apoptotic cells. Intraperitoneal injection of lipidoid-formulated CLDN3 siRNA resulted in a substantial reduction in tumor burden in MISIIR/TAg transgenic mice and mice bearing tumors derived from mouse ovarian surface epithelial cells. Ascites development was reduced in CLDN3 siRNA-treated mice, suggesting the treatment effectively suppressed metastasis. Toxicity was not observed after multiple i.p. injections. Importantly, treatment of mice with nonimmunostimulatory 2′-OMe modified CLDN3 siRNA was as effective in suppressing tumor growth as unmodifed siRNA. These results suggest that lipidoid-formulated CLDN3 siRNA has potential as a therapeutic for ovarian cancer.

Nanoparticle-Delivered Suicide Gene Therapy Effectively Reduces Ovarian Tumor Burden in Mice

There is currently no effective therapy for patients with advanced ovarian cancer. To address the need for a more effective treatment for this deadly disease, we conducted preclinical tests in ovarian tumor-bearing mice to evaluate the therapeutic efficacy of using a cationic biodegradable poly(beta-amino ester) polymer as a vector for nanoparticulate delivery of DNA encoding a diphtheria toxin suicide protein (DT-A). The promoter sequences of two genes that are highly active in ovarian tumor cells, MSLN and HE4, were used to target DT-A expression to tumor cells. Administration of DT-A nanoparticles directly to s.c. xenograft tumors and to the peritoneal cavity of mice bearing primary and metastatic ovarian tumors resulted in a significant reduction in tumor mass and a prolonged life span compared to control mice. Minimal nonspecific tissue and blood chemistry toxicity was observed following extended treatment with nanoparticles. DT-A nanoparticle therapy suppressed tumor growth more effectively than treatment with clinically relevant doses of cisplatin and paclitaxel. Our findings suggest that i.p. administration of polymeric nanoparticles to deliver DT-A encoding DNA, combined with transcriptional regulation to target gene expression to ovarian tumor cells, holds promise as an effective therapy for advanced-stage ovarian cancer.

Rapid Optimization of Gene Delivery by Parallel End-modification of Poly(β-amino ester)s

Poly(β-amino ester)s are cationic degradable polymers that have significant potential as gene delivery vectors. Here we present a generalized method to modify poly(β-amino ester)s at the chain ends to improve their delivery performance. End-chain coupling reactions were developed so that polymers could be synthesized and tested in a high-throughput manner, without the need for purification. In this way, many structural variations at the polymer terminus could be rapidly evaluated. End-modification of the terminal amine structure of a previously optimized poly(β-amino ester), C32, significantly enhanced its in vitro transfection efficiency. In vivo, intraperitoneal (IP) gene delivery using end-modified C32 polymers resulted in expression levels over one order of magnitude higher than unmodified C32 and jet-polyethylenimine (jet-PEI) levels in several abdominal organs. The rapid end-modification strategy presented here has led to the discovery of many effective polymers for gene delivery and may be a useful method to develop and optimize cationic polymers for gene therapy.

Absence of Mycobacterium intracellulare and Presence of Mycobacterium chimaera in Household Water and Biofilm Samples of Patients in the United States with Mycobacterium avium Complex Respiratory Disease

ABSTRACT Recent studies have shown that respiratory isolates from pulmonary disease patients and household water/biofilm isolates of Mycobacterium avium could be matched by DNA fingerprinting. To determine if this is true for Mycobacterium intracellulare, household water sources for 36 patients with Mycobacterium avium complex (MAC) lung disease were evaluated. MAC household water isolates from three published studies that included 37 additional MAC respiratory disease patients were also evaluated. Species identification was done initially using nonsequencing methods with confirmation by internal transcribed spacer (ITS) and/or partial 16S rRNA gene sequencing. M. intracellulare was identified by nonsequencing methods in 54 respiratory cultures and 41 household water/biofilm samples. By ITS sequencing, 49 (90.7%) respiratory isolates were M. intracellulare and 4 (7.4%) were Mycobacterium chimaera. In contrast, 30 (73%) household water samples were M. chimaera, 8 (20%) were other MAC X species (i.e., isolates positive with a MAC probe but negative with species-specific M. avium and M. intracellulare probes), and 3 (7%) were M. avium; none were M. intracellulare. In comparison, M. avium was recovered from 141 water/biofilm samples. These results indicate that M. intracellulare lung disease in the United States is acquired from environmental sources other than household water. Nonsequencing methods for identification of nontuberculous mycobacteria (including those of the MAC) might fail to distinguish closely related species (such as M. intracellulare and M. chimaera). This is the first report of M. chimaera recovery from household water. The study underscores the importance of taxonomy and distinguishing the many species and subspecies of the MAC.

K6/ODC transgenic mice as a sensitive model for carcinogen identification

Ornithine decarboxylase (ODC), an important enzyme in the polyamine biosynthetic pathway, is aberrantly regulated in many epithelial tumors of rodents and humans. In murine skin, it has been shown that ODC overexpression provides a sufficient condition for tumor promotion. Therefore, we hypothesized that K6/ODC transgenic mice in which ODC overexpression was targeted to hair follicle keratinocytes might provide a sensitive model for identifying genotoxic carcinogens. Ten known carcinogens or noncarcinogens have been tested in the model so far and results are highly concordant with 2-year rodent bioassays (100% concordant). More importantly, each of two chemicals tested that is recognized as a human carcinogen was identified as a carcinogen in K6/ODC transgenic mice. In addition, 7, 12-dimethylbenz(a)anthracene (DMBA) dose response studies indicated that even at a very low dose, 2 nmol, a high percentage of mice (50%) had already developed tumors 8 weeks after treatment. We conclude that the K6/ODC transgenic mouse model is very sensitive to topical application of genotoxic carcinogens and could therefore be a useful mouse model for carcinogen identification and chemical risk assessment.

Nanoparticulate delivery of diphtheria toxin DNA effectively kills Mesothelin expressing pancreatic cancer cells

Pancreatic cancer is the fourth leading cause of cancer-related deaths in this country, and there is currently no effective targeted treatment for this deadly disease. A dire need exists to rapidly translate our molecular understanding of this devastating disease into effective, novel therapeutic options. Mesothelin is a candidate target protein shown by a number of laboratories to be specifically overexpressed in pancreatic cancers and not in the adjacent normal tissue. Translational investigations have shown promising results using this molecule as a therapeutic target (e.g., vaccine strategies). In addition, the mesothelin promoter has been cloned and dissected and can therefore be used as a vehicle for regulating expression of DNA sequences. Using a novel, proven, biodegradable nanoparticulate system, we sought to target mesothelin-expressing pancreatic cancer cells with a potent suicide gene, diphtheria toxin-A (DT-A). We first confirmed reports that a majority of pancreatic cancer cell lines and resected pancreatic ductal adenocarcinoma specimens overexpressed mesothelin at the mRNA and protein levels. High mesothelin-expressing pancreatic cancer cell lines produced more luciferase than cell lines with undetectable mesothelin expression when transfected with a luciferase sequence under the regulation of the mesothelin promoter. We achieved dramatic inhibition of protein translation (>95%) in mesothelin-expressing pancreatic cancer cell lines when DT-A DNA, driven by the mesothelin promoter, was delivered to pancreatic cancer cells. We show that this inhibition effectively targets the death of pancreatic cancer cells that overexpress mesothelin. The work presented here provides evidence that this strategy will work in pre-clinical mouse pancreatic cancer models, and suggests that such a strategy will work in the clinical setting against the majority of pancreatic tumors, most of which overexpress mesothelin.

Mitoxantrone Targets Human Ubiquitin-Specific Peptidase 11 (USP11) and Is a Potent Inhibitor of Pancreatic Cancer Cell Survival

Pancreatic ductal adenocarcinoma (PDA) is the fourth leading cause of cancer-related death in the United States, with a 95% five-year mortality rate. For over a decade, gemcitabine (GEM) has been the established first-line treatment for this disease despite suboptimal response rates. The development of PARP inhibitors that target the DNA damage repair (DDR) system in PDA cells has generated encouraging results. Ubiquitin-specific peptidase 11 (USP11), an enzyme that interacts with the DDR protein BRCA2, was recently discovered to play a key role in DNA double-strand break repair and may be a novel therapeutic target. A systematic high-throughput approach was used to biochemically screen 2,000 U.S. Food and Drug Administration (FDA)-approved compounds for inhibition of USP11 enzymatic activity. Six pharmacologically active small molecules that inhibit USP11 enzymatic activity were identified. An in vitro drug sensitivity assay demonstrated that one of these USP11 inhibitors, mitoxantrone, impacted PDA cell survival with an IC50 of less than 10 nM. Importantly, across six different PDA cell lines, two with defects in the Fanconi anemia/BRCA2 pathway (Hs766T and Capan-1), mitoxantrone is 40- to 20,000-fold more potent than GEM, with increased endogenous USP11 mRNA levels associated with increased sensitivity to mitoxantrone. Interestingly, USP11 silencing in PDA cells also enhanced sensitivity to GEM. These findings establish a preclinical model for the rapid discovery of FDA-approved compounds and identify USP11 as a target of mitoxantrone in PDA. Implications: This high-throughput approach provides a strong rationale to study mitoxantrone in an early-phase clinical setting for the treatment of PDA. Mol Cancer Res; 11(8); 901–11. ©2013 AACR.

Essential role for Abi1 in embryonic survival and WAVE2 complex integrity

Abl interactor 1 (Abi1) plays a critical function in actin cytoskeleton dynamics through participation in the WAVE2 complex. To gain a better understanding of the specific role of Abi1, we generated a conditional Abi1-KO mouse model and MEFs lacking Abi1 expression. Abi1-KO cells displayed defective regulation of the actin cytoskeleton, and this dysregulation was ascribed to altered activity of the WAVE2 complex. Changes in motility of Abi1-KO cells were manifested by a decreased migration rate and distance but increased directional persistence. Although these phenotypes did not correlate with peripheral ruffling, which was unaffected, Abi1-KO cells exhibited decreased dorsal ruffling. Western blotting analysis of Abi1-KO cell lysates indicated reduced levels of the WAVE complex components WAVE1 and WAVE2, Nap1, and Sra-1/PIR121. Although relative Abi2 levels were more than doubled in Abi1-KO cells, the absolute Abi2 expression in these cells amounted only to a fifth of Abi1 levels in the control cell line. This finding suggests that the presence of Abi1 is critical for the integrity and stability of WAVE complex and that Abi2 levels are not sufficiently increased to compensate fully for the loss of Abi1 in KO cells and to restore the integrity and function of the WAVE complex. The essential function of Abi1 in WAVE complexes and their regulation might explain the observed embryonic lethality of Abi1-deficient embryos, which survived until approximately embryonic day 11.5 and displayed malformations in the developing heart and brain. Cells lacking Abi1 and the conditional Abi1-KO mouse will serve as critical models for defining Abi1 function.

Conversion of C57Bl/6 mice from a tumor promotion–resistant to a –sensitive phenotype by enhanced ornithine decarboxylase expression

A transgenic mouse model was developed in which ornithine decarboxylase (ODC) can be overexpressed in a tissue‐specific and regulated manner. Hair follicle keratinocytes were targeted by use of a bovine keratin 6 (K6) promoter/regulatory region, and regulation was accomplished by using the tetracycline‐regulated transactivator/tetracycline‐response element system. Double‐transgenic mice carrying both transgenes (K6/tetracycline‐regulatable transactivator protein (tTA) and tetracycline‐response element/Odc) on a C57Bl/6 background had no obvious phenotypic abnormalities in the absence (Odc transgene–expressed) of doxycycline (a tetracycline analog) in the drinking water. However, induction of K6‐driven tTA expression by the tumor promoter (12‐O‐tetradecanoylphorbol‐13‐acetate) (TPA) led to very high levels of epidermal ODC activity and robust hyperplasia, especially involving hair follicles. Both effects were abolished by inclusion of doxycycline in the drinking water to repress transgene expression. Finally, the number of papillomas that developed in a standard (7,12‐dimethybenz[a]anthracene) (DMBA)/TPA protocol was greatly reduced in mice in which transgenic Odc expression was repressed by doxycycline. Our results demonstrated that the higher levels of ODC expression produced in the transgenic model in the induced versus the repressed condition make the normally promotion‐resistant C57Bl/6 strain much more sensitive to the short‐term and long‐term (i.e., tumor‐promoting) effects of TPA. Mol. Carcinog. 26:32–36, 1999.

The mRNA-binding protein HuR promotes hypoxia-induced chemoresistance through posttranscriptional regulation of the proto-oncogene PIM1 in pancreatic cancer cells.

Previously, it has been shown that pancreatic ductal adenocarcinoma (PDA) tumors exhibit high levels of hypoxia, characterized by low oxygen pressure (pO2) and decreased O2 intracellular perfusion. Chronic hypoxia is strongly associated with resistance to cytotoxic chemotherapy and chemoradiation in an understudied phenomenon known as hypoxia-induced chemoresistance. The hypoxia-inducible, pro-oncogenic, serine–threonine kinase PIM1 (Proviral Integration site for Moloney murine leukemia virus 1) has emerged as a key regulator of hypoxia-induced chemoresistance in PDA and other cancers. Although its role in therapeutic resistance has been described previously, the molecular mechanism behind PIM1 overexpression in PDA is unknown. Here, we demonstrate that cis-acting AU-rich elements (ARE) present within a 38-base pair region of the PIM1 mRNA 3′-untranslated region mediate a regulatory interaction with the mRNA stability factor HuR (Hu antigen R) in the context of tumor hypoxia. Predominantly expressed in the nucleus in PDA cells, HuR translocates to the cytoplasm in response to hypoxic stress and stabilizes the PIM1 mRNA transcript, resulting in PIM1 protein overexpression. A reverse-phase protein array revealed that HuR-mediated regulation of PIM1 protects cells from hypoxic stress through phosphorylation and inactivation of the apoptotic effector BAD and activation of MEK1/2. Importantly, pharmacological inhibition of HuR by MS-444 inhibits HuR homodimerization and its cytoplasmic translocation, abrogates hypoxia-induced PIM1 overexpression and markedly enhances PDA cell sensitivity to oxaliplatin and 5-fluorouracil under physiologic low oxygen conditions. Taken together, these results support the notion that HuR has prosurvival properties in PDA cells by enabling them with growth advantages in stressful tumor microenvironment niches. Accordingly, these studies provide evidence that therapeutic disruption of HuR’s regulation of PIM1 may be a key strategy in breaking an elusive chemotherapeutic resistance mechanism acquired by PDA cells that reside in hypoxic PDA microenvironments.